The invention relates to an additive composition for two-cycle oils and concentrates containing said additive package and a method of preparing the additive composition or concentrates. The additive composition, when incorporated into two-cycle oils, provides greatly improved engine cleanliness, particularly with regard to ring sticking, and improved lubricity and antiwear performance.
Two-cycle (two-stroke) internal combustion engines, including rotary engines are found in power lawn mowers and other power-operated gardening equipment, power chain saws, pumps, electrical generators, marine outboard engines, snowmobiles, motorcycles, and the like. Two-cycle engines employed as such are operated by mixing the fuel and the two-cycle oil in prescribed proportions. The two-cycle oil additive of the instant invention is designed for use in most types of two-cycle engines and particularly in water-cooled marine outboard engines.
Two-cycle engines are lubricated by mixing the lubricant with the fuel for the engine. The mixture of fuel and lubricant passes through the crankcase of a two-cycle engine, where it lubricates the moving parts in the lower portion of the engine and then flows through intake ports into the combustion chamber. There it lubricates the cylinder zone of the engine and is burned. The combustion products are vented from the combustion chambers through exhaust ports. As a consequence, a satisfactory lubricant for a two-cycle engine must not only provide adequate lubrication for moving engine parts but also must be able to pass into the combustion chamber leaving no objectionable deposits in the intake ports; must burn cleanly to avoid fouling the combustion chamber and spark plug with undesirable deposits; control varnish and sludge formation which leads to ring sticking and in turn to failure of the sealing function of piston rings; and must not result in plugging of the exhaust ports.
The increasing severity of the conditions under which two-cycle engines operate has led to increasing demands for oils to adequately lubricate such engines. Alleviation of the problems has been through the provision of more effective additives for two-cycle engine oils and oil fuel combinations.
The largest and most expensive two-cycle engines are the water-cooled outboards used in marine applications. Engines with up to six cylinders and horse-power ratings to 300 are now available.
In recent years, these engines have shown an increasing tendency towards premature failure via deposit related piston-ring sticking. This may be in part due to a deterioration in fuel quality, both in terms of deposit forming tendency and motor octane number, which has occurred in some areas of the United States as a result of the change to unleaded fuel. Engine changes aimed at increased out-put, improved fuel economy and reduced emissions also may have aggravated the ring sticking problem.
It is known to use acylated nitrogen-containing compounds as dispersants in two-cycle lubricants to prevent the deposition of solid materials on engine surfaces in contact with the lubricating composition. Such acylated nitrogen-containing compounds, as for instance the reaction product of isostearic acid and a polyamine, are disclosed in U.S. Pat. No. 3,110,673 and 4,705,643.
U.S. Pat. No. 3,110,673 mentioned above discloses a lubricant composition containing a pour point depressant and ashless dispersant. The ashless dispersant is described as the reaction product of a polyalkylene amine and a mixed, branched and straight chain acid.
U.S. Pat. No. 4,705,643 also briefly discussed above described an ashless lubricating two-cycle oil-additive comprised of the condensation reaction product of a branched isostearic acid and tetraethylene pentamine.
U.S. Pat. No. 2,568,876 discloses the use of organic nitrogen compounds as corrosion inhibiting compositions. The organic nitrogen compound disclosed are reaction products of monocarboxylic acids and polyalkylene polyamines having one more nitrogen atom per molecule than there are alkylene groups in the molecule, which are further reacted with an alkenyl succinic acid anhydride. The ratio of alkenyl succinic acid to monocarboxylic acid disclosed is 1:1 to 4:1 and the alkenyl radical carbon range disclosed preferably range from 8 to 18.
U.S. Pat. No. 3,216,936 discloses nitrogen-containing compositions derived from the acylation of alkylene amines and is used to stabilize metal phosphorodithioates antioxidant additives in lubricating compositions. The acylated amines of the patent are prepared by heating together an alkylene amine with an acidic mixture consisting of a hydrocarbon-substituted succinic acid and an aliphatic monocarboxylic acid. The equivalent amount of succinic acid to monocarboxylic acid disclosed range from 1:0.1 to about 1:1.
U.S. Pat. Nos. 4,200,545; 4,708,809; 4,663,063; 4,708,809 and 4,780,111 all disclosed products derived from reacting first and second acylating agents comprising carboxylic acids or anhydrides with polyamines wherein the range of equivalence for the succinic acid agent to monocarboxylic acid ranges from 1:1 to 10:1.
The present invention is directed to an additive for two-cycle lubricating oils especially two-cycle oil additives for water-cooled outboard engines. The invention is further directed to an additive which is stable at low temperatures and which also provides good detergency, lubricity, antiwear and corrosion inhibition.
Copending application U.S. Ser. No. 742,955, filed Aug. 9, 1991, discloses controlling gel formation in two-cycle oil with an additive comprising a reaction product of a monocarboxylic acid, a polyalkylene polyamine and a high molecular weight acylating agent. The application further disclosed additive compositions also containing a polyolefin and a pour point depressant flow improver. Applications Docket Nos. PT-911 and PT-913 filed contemporoneously with the instant application disclosed respectively amide/imidazoline dispersants and amide/imide/imidazoline dispersants used in combination with alcohols and/or wax crystal modifiers to control gel formation in two-cycle oils. Both disclosures are incorporated herein by reference.